A method for detecting organic phosphorus residues in medicinal and edible products based on paper spray mass spectrometry

Abstract

The application discloses a method for detecting organic phosphorus residues in a medicine-food homologous product based on a paper spray mass spectrometry technology, and belongs to the technical field of paper adsorption mass spectrometry detection. The method is specifically as follows: a to-be-detected sample is weighed and dispersed in an acetic acid aqueous solution, dichloromethane is added after ultrasonic treatment, oscillation, centrifugation and recovery of an organic layer are performed, and a to-be-detected solution is obtained; then, a COF-300 paper base is placed in the to-be-detected solution for extraction, the paper base is dried after extraction, and a spraying solvent ethanol is added dropwise on the COF-300 paper base; a QTRAP 4500 mass spectrometry system is used for detection; and the content of OPPs in the to-be-detected sample is calculated according to a detection result and a standard curve. The method has good sensitivity, accuracy and repeatability, has the advantages of high efficiency, rapidness and small solvent usage, improves the food safety monitoring efficiency, meets the environmental protection requirements, and has important popularization value.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for detecting organic phosphorus residues in medicinal and edible products based on paper spray mass spectrometry, belonging to the field of paper adsorption mass spectrometry. BACKGROUND

[0002] The problem of organic phosphorus pesticide residues in medicinal and edible substances and corresponding products has attracted widespread attention in recent years. Organic phosphorus pesticides are known for their strong neurotoxicity, and accumulation in food can lead to a series of health problems, including acute poisoning and long-term chronic diseases, so it is particularly important to ensure food safety.

[0003] Currently, the mainstream methods for detecting organic phosphorus residues mainly include gas chromatography (GC), gas chromatography mass spectrometry (GC-MS / MS), liquid chromatography (LC), and liquid chromatography mass spectrometry (LC-MS / MS). These techniques perform well in terms of sensitivity, accuracy, and quantitative analysis capabilities, and can effectively identify and quantify multiple organic phosphorus pesticide components. However, despite the significant advantages of these chromatography and mass spectrometry methods in detection applications, there are still some limitations in actual operation: first, the operation process of these methods is usually complex, requiring professional personnel to perform delicate sample pretreatment and instrument debugging, which not only increases the operation difficulty, but also puts forward higher requirements for the skill level of laboratory personnel. Secondly, during the sample pretreatment process, a large amount of chemical solvent is often required, which not only increases the detection cost, but also may cause environmental burden. In addition, the detection period is relatively long, often leading to the inability to quickly feedback the detection results, thereby affecting the timely monitoring and risk assessment of food safety.

[0004] In view of the challenges faced by current detection methods, it is particularly important to develop a rapid, simple and low-pollution detection technology. This technology should not only simplify the operation process, but also minimize the impact on the environment, while providing rapid and accurate detection results. In addition, the cost factor is also crucial. An ideal food safety detection technology needs to consider rapidity, simplicity, low pollution, high performance and low cost (including reagents, instruments, consumables and labor cost), making it economically feasible and easy to promote. Such technological progress will significantly improve the efficiency of food safety monitoring, providing consumers with more timely and reliable information protection, and has important practical significance and wide application value. SUMMARY

[0005] To address the shortcomings and deficiencies of existing technologies, the present invention aims to provide a method for detecting organophosphorus residues in food and medicinal products based on paper spray mass spectrometry. The core of this method lies in utilizing the excellent adsorption properties of covalent organic frameworks (COFs) to effectively capture organophosphorus residues in food and medicinal products. The sample is simply sprayed onto COFs paper, and after simple pretreatment, it can be placed into a mass spectrometer for analysis. Compared with traditional detection methods, this method not only achieves rapid and efficient detection, eliminating the need for pretreatment and purification processes and significantly reducing reagent consumption, but also effectively reduces the generation of chemical waste. This technical solution can better address food safety challenges and provide consumers with more reliable protection.

[0006] To achieve the above objectives, the following technical solution is provided:

[0007] This invention provides a method for detecting organophosphorus residues in food and medicine homologous products based on paper spray mass spectrometry, the method comprising the following steps:

[0008] (1) Sample pretreatment

[0009] Weigh the sample to be tested and disperse it in an aqueous acetic acid solution. After sonication, add dichloromethane, shake, centrifuge, and recover the organic layer to obtain the test solution.

[0010] (2) Determination of organic phosphorus content in the sample to be tested

[0011] The COF-300@paper base was extracted by placing it into the test solution in step (1). After extraction, it was dried and ethanol was added dropwise onto the COF-300@paper base. Then, the mass spectrometry system was used for detection. The content of OPPs in the test sample was calculated based on the detection results and the standard curve.

[0012] In one embodiment, the organophosphorus includes one or more of phosmet, phosmet, dimethoate, phosmet, and acephate.

[0013] In one embodiment, the food-medicine homology product includes one or more of the following: hawthorn, ginseng and coix seed tea, red ginseng and rose vitality tea, red ginseng, rose and dandelion tea, goji berries, and ginseng.

[0014] In one embodiment, the volume fraction of the acetic acid aqueous solution in step (1) is 1-5%.

[0015] In one embodiment, the mass-to-volume ratio of the sample to be tested, the aqueous acetic acid solution, and the dichloromethane in step (1) is 1:20-30:10-20; g:mL:mL.

[0016] In one embodiment, the centrifugation parameters in step (1) are 5000-8000 rpm and the time is 5-10 min.

[0017] In one embodiment, the COF-300@paper base in step (2) is specifically obtained by mixing COF-300 powder with ultrapure water, sonicating to obtain a uniformly dispersed suspension, transferring it to a Buchner funnel containing filter paper, filtering under vacuum conditions, and then naturally drying the COF-300-loaded filter paper matrix at room temperature to obtain COF-300@paper; then cutting the COF-300@paper into isosceles triangles to obtain isosceles triangle COF-300@paper base.

[0018] In one embodiment, the amount of COF-300 loaded on each 3.5cm diameter filter paper on the COF-300@paper base is 2.5 to 12.5 mg; preferably, the amount of COF-300 loaded on each 3.5cm diameter filter paper is 5 mg.

[0019] In one embodiment, the COF-300@paper base in step (2) is an isosceles triangle with a height of 10-15cm and a apex angle of 10-60°, preferably 30°.

[0020] In one embodiment, the COF-300 powder is prepared by using terephthalaldehyde (BDA) and tetrakis(4-aminophenyl)methane (TAM) as monomers and allowing them to react at a temperature of 40-45°C for 36-48 hours.

[0021] In one embodiment, the specific preparation method of the COF-300 powder is as follows:

[0022] (1) Mix BDA, 1,4-dioxane and CF3CH2NH2, vortex, and add CF3COOH to obtain reaction solution A;

[0023] (2) Dissolve TAM in 1,4-dioxane to obtain reaction solution B;

[0024] (3) Add reaction solution B to reaction solution A, filter, and let stand at 40-45℃ for 36-48h. After the reaction is completed, extract the synthesized crystals in 1,4-dioxane and tetrahydrofuran by Soxhlet extraction, dry, and obtain yellow crystals, namely COF-300.

[0025] In one embodiment, the mass ratio of BDA to TAM is 10 to 15:20.

[0026] In one embodiment, the parameters of the mass spectrometry system used in step (2) are as follows: QTRAP 4500 mass spectrometry system, with the following mass spectrometry parameters: curtain gas: 10 psi; ion source gas 1: 0 Psi; ion source gas 2: 0 Psi; spray voltage 3400 V; IHT (Ion Guide Heater Temperature): 150 °C; collision gas: nitrogen; inlet voltage: 10 V; outlet voltage: 10 V; multiple reaction monitoring (MRM) positive ion mode scanning, scan rate of 10 Da / s; paper angle of 30°.

[0027] The present invention also provides the application of the above-described method in food safety monitoring.

[0028] Beneficial effects:

[0029] This invention provides a method for detecting organophosphorus residues in food and medicine homologous products based on paper spray mass spectrometry, which has the following significant advantages:

[0030] (1) High selectivity and adsorption capacity: The excellent adsorption properties of COFs paper significantly improve the sensitivity and accuracy of detection;

[0031] (2) Simple and fast operation process: Paper spray mass spectrometry is simple to operate and does not require a complicated sample pretreatment and purification process, which can effectively shorten the detection time;

[0032] (3) Environmentally friendly and low cost: This method uses less solvent during the detection process, minimizes environmental pollution, and can be reused 5 times.

[0033] (4) High efficiency: It can be applied to the simultaneous real-time detection of a variety of organophosphorus pesticides, and is suitable for rapid qualitative and quantitative analysis at the grassroots level.

[0034] This invention enables the rapid detection of organophosphorus compounds in various food and medicinal substances and products. The results show that the method has good sensitivity, accuracy and repeatability, further verifying its potential for wide application in food safety monitoring. While improving the efficiency of food safety monitoring, it also takes into account environmental protection requirements and has important promotional value.

[0035] Furthermore, this method exhibits low limits of detection and quantitation, and boasts advantages such as high efficiency, speed, and low solvent consumption. Specifically, for five organophosphorus pesticides (OPPs), approximately 90% equilibrium adsorption can be achieved using COF-300 material within about 5 minutes. This method also features simple operation and low matrix effect, making it suitable for the analysis of OPP residues in complex food matrix samples, thus providing effective assurance for food safety. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the synthesis of the COF-300 material prepared in Example 1;

[0037] Figure 2 The XRD pattern of the COF-300 material prepared in Example 1;

[0038] Figure 3 The PT-IR spectrum of the COF-300 material prepared in Example 1;

[0039] Figure 4 (a) Nitrogen adsorption-desorption isotherm of COF-300 material prepared in Example 1; (b) BET specific surface area of ​​COF-300; (c) Pore size distribution of COF-300.

[0040] Figure 5 Schematic diagram of the molecular diameters of 5 types of OPPs;

[0041] Figure 6 The stability of the COF-300 material prepared in Example 1 in different solvents is shown in the figure.

[0042] Figure 7 The adsorption kinetic model diagrams for the COF-300 material prepared in Example 1 are shown below: (a) pseudo-first-order kinetic model; (b) pseudo-second-order kinetic model; (c) relationship between OPPs adsorption amount and time.

[0043] Figure 8 A schematic diagram of the process for preparing the COF-300@paper paper base in Example 2;

[0044] Figure 9 Scanning electron microscope (SEM) images of the COF-300@paper paper substrate prepared in Example 2; (a) filter paper; (b) COF-300@paper at different magnifications (100 μm); (c) COF-300@paper at different magnifications (50 μm); (d) COF-300@paper after 5 PSI tests;

[0045] Figure 10 XPS spectra of COF-300@paper before and after adsorption of OPPs prepared in Example 2; (a) High-resolution C1s XPS spectra of COF-300 before and after adsorption of 5 kinds of OPPs; (b) High-resolution P2p XPS spectra of COF-300 before and after adsorption of 5 kinds of OPPs; (c) High-resolution S2p XPS spectra of COF-300 before and after adsorption of 5 kinds of OPPs.

[0046] Figure 11 This is a flowchart illustrating the detection method in Example 3;

[0047] Figure 12 Standard curves for 5 OPPs; (a) fenthion in 0.5-200 μg·L -1 (a) Standard curve equation and correlation coefficient within the range; (b) Phosphate in the range of 0.5-200 μg·L -1 (c) Standard curve equation and correlation coefficient within the range of 0.5-200 μg·L⁻¹; -1 Standard curve equations and correlation coefficients within the range; (d) Iminephos in 0.5-200 μg·L -1 Standard curve equations and correlation coefficients within the range; (e) acephate in the range of 0.5-200 μg·L⁻¹ -1 The standard curve equation and correlation coefficient within the specified range;

[0048] Figure 13 The stability and repeatability of the COF-300@paper base prepared in Example 2 are shown in the figures: (a) Stability after storage for different numbers of days; (b) Repeatability.

[0049] Figure 14 Data plots optimized for different parameters; (a) different COF-300 loading; (b) different spray voltage; (c) different spray solvent; (d) different tip angle. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0051] The testing method involved in this invention:

[0052] 1. PXRD: The COF-300 sample was uniformly filled into the wafer groove using a glass slide, and X-ray diffraction analysis was performed using a Cu-Kα radiation source. Instrument parameters were set as follows: scan step size 0.05°, dwell time per step 0.5 seconds, and scan angle range 2-40°. The obtained diffraction data were plotted with 2θ angle as the x-axis and diffraction intensity as the y-axis, and finally processed and plotted using Origin software.

[0053] 2. FT-IR: The infrared characteristics of terephthalaldehyde (BDA), tetrakis(4-aminophenyl)methane (TAM), synthesized COF-300, and COF-300 after saturation adsorption of OPPs were determined using Fourier transform infrared spectroscopy. The test temperature was set to 25℃, and the resolution was 0.5 cm⁻¹. -1 Wavenumber range 4000–500 cm⁻¹ -1 The results were plotted using wavenumber on the x-axis and transmittance on the y-axis, and analyzed using Origin software.

[0054] 3. SEM: The morphology of blank filter paper, COF-300@paper, and COF-300@paper after 5 spray ionization treatments was characterized by scanning electron microscopy, and the results were observed at different magnifications.

[0055] 4. N2 adsorption-desorption experiment: The specific surface area and pore size distribution of the synthesized COF-300 were measured using a gas adsorption instrument.

[0056] 5. XPS: X-ray photoelectron spectroscopy was used to determine the full spectrum and high-resolution C1s, P2p, and S2p spectra of COF-300 before and after adsorption of five OPPs. This verified the binding type and elemental composition of the material.

[0057] Example 1

[0058] The preparation method of single-crystal COF-300 material includes the following steps:

[0059] (1) Add terephthalaldehyde BDA (12 mg, 0.089 mmol), 1,4-dioxane (0.50 mL), and CF3CH2NH2 (70 μL, 10 mol / L) to a 5.0 mL sample bottle in sequence. After vortexing, add 0.10 mL of CF3COOH (6.0 mol / L) to obtain reaction solution A.

[0060] (2) Tetra(4-aminophenyl)methane (TAM) (20 mg, 0.052 mmol) was dissolved in 1,4-dioxane (0.50 mL) to obtain reaction solution B;

[0061] (3) Add reaction solution B to reaction solution A, filter through a 0.20 μm nylon-6 membrane, and let stand at 40 °C for 48 h. After the reaction is complete, extract the synthesized crystals in 1,4-dioxane and tetrahydrofuran respectively by Soxhlet extraction for 1 day each. After drying under vacuum at 120 °C for 12 h, yellow crystals, namely COF-300, are obtained (synthesis schematic diagram shown). Figure 1 As shown in the figure, the yield was 65%.

[0062] Characterization of COF-300 material:

[0063] 1. The crystal structure of the prepared COF-300 was analyzed by PXRD.

[0064] The results are as follows Figure 2 As shown, the main peak of COF-300 is in the low-angle region (2θ=8.8°), showing a sharp diffraction peak. The main peak corresponds to the (100) crystal plane, reflecting the cell parameter aa8. According to the Bragg equation (Equations 1 and 2).

[0065] nλ=2d(hkl)sinθ (1)

[0066]

[0067] Where n represents the diffraction number, λ represents the wavelength of the incident X-ray, d(hkl) represents the spacing between the (hkl) crystal planes in the crystal, θ represents the angle between the incident X-ray and the reflecting surface, a represents the lattice constant, and h, k, and l represent the crystal plane indices, respectively.

[0068] The second peak (12.5°–12.8°) corresponds to the (110) crystal plane, and θ(110) ≈ 12.6° can be derived using the Bragg equation (assuming α is determined by the 8.8° main peak). The third peak (17.8°–18.0°) corresponds to the (200) crystal plane, and θ(200) ≈ 17.8° is calculated. The specific angles may fluctuate slightly due to differences in cell parameters, indicating its highly ordered periodic framework structure. Characteristic diffraction peaks with lower intensity are at 20.8° and 24.3°, which is consistent with the literature reports, proving that COF-300 is a crystalline polymer.

[0069] 2. The crystal structure of the prepared COF-300 was characterized by FT-IR spectroscopy.

[0070] result Figure 3 As shown in the FT-IR spectra, comparing the spectra of BDA, TAM, and COF-300, it was found that in the COF-300 spectrum, the 1685 cm⁻¹... -1 and 3395cm -1 The characteristic peak at this point was significantly weakened, and a peak at 1620 cm⁻¹ appeared. -1 The new peak at this location. This means that C=O (1685cm) in BDA. -1 ) key and TAM (3395cm -1 The NH bond in the ) underwent an amine-aldehyde condensation reaction, forming C=N (1620cm) -1 The discovery of new bonds provides some evidence of the successful synthesis of COF-300. Furthermore, the almost unchanged FT-IR spectrum of COF-300 after saturation adsorption of various OPPs demonstrates that OPPs have virtually no effect on disrupting the imine bonds of COF-300.

[0071] 3. Characterization using a nitrogen adsorption meter

[0072] The specific surface area and pore size distribution of COF-300 were analyzed by N2 adsorption-desorption experiments at 77K. The results... Figure 4 As shown, from Figure 4 As shown in (a) and (c), COF-300 exhibits a sharp increase in N2 absorption below a relative pressure of 0.2, and a narrow pore size distribution around 1.9 nm, confirming that COF-300 has a microporous structure. Its specific surface area (BET) is 175.496 m². 2 ·g -1 The pore size is 1.98 nm. The results show that the synthesized COF-300 material has the characteristics of large surface area and porosity.

[0073] The molecular diameters of OPPs (phosmet, phosmet, dimethoate, phosmet, and acephate) measured by ChemDraw 3D software simulation ( Figure 5 The pore sizes are 1.1 nm, 1.4 nm, 1.0 nm, 1.3 nm and 0.6 nm, respectively, all smaller than the pore size of COF-300. Therefore, pore size selection can occur, providing conditions for the subsequent use of COF-300 material for OPPs detection.

[0074] 4. Chemical stability test

[0075] 25 mg of COF-300 sample was weighed and placed in a 2 mL centrifuge tube. 1 mL of different chemical solvents (THF, H₂O, EtOH, iPrOH, n-Hex solvent) were added to each tube. After standing in the dark for 24 hours, the sample was centrifuged at 8000 rpm for 5 minutes to separate the solid and liquid phases. The supernatant was discarded, and the precipitate was then placed in a 60℃ vacuum drying oven for 12 hours (the centrifuge tube opening was sealed with pinhole aluminum foil). Finally, the crystal structure integrity of the dried solid was analyzed by PXRD, and the data processing method followed the standard PXRD analysis procedure.

[0076] The results are as follows Figure 6 As shown, the crystal COF-300 can still maintain its original crystal form in THF, H2O, EtOH, iPrOH and n-Hex solvents, indicating that the crystal COF-300 has a certain degree of chemical stability in the above solvents and can be used as COF-300@paper adsorbent material.

[0077] 5. Adsorption kinetics evaluation

[0078] The adsorption process of COF-300 for five OPPs was evaluated using adsorption kinetic models, including pseudo-first-order and pseudo-second-order kinetic models. The first-order kinetic model (Equation 3) and the pseudo-second-order kinetic model (Equation 4) were fitted. The model formulas are as follows:

[0079] ln(q e -q t )=ln q e -k1t (3)

[0080]

[0081] Where qe and qt are the adsorption amounts (μg·g) of the target analyte at equilibrium and at a certain time t, respectively. -1 k1 and k2 are the rate constants of the pseudo-first-order and pseudo-second-order dynamic models, respectively; the parameters are shown in Table 1:

[0082] Table 1 Kinetic parameters of COF-300 adsorption of 5 OPPs

[0083]

[0084] The results are as follows Figure 7 As shown, when the initial concentration is 200 μg·L -1 At that time, the adsorption process of OPPs by COF-300 is more in line with the pseudo-second-order kinetic model (R²). 2 >R1 2 COF-300 exhibits rapid adsorption of all five OPP targets within a short period of time, reaching approximately 90% of the OPP equilibrium adsorption capacity within 5 minutes.

[0085] The maximum adsorption capacities of COF-300 for phosmet, phosmet, dimethoate, phosmet, and acephate were 132.45 μg·g. -1 139.66 μg·g -1 632.91 μg·g -1 127.06 μg·g -1 301.20 μg·g -1 This may be due to the different chemical structures of the five OPPs and the varying strengths of their interactions with COF-300, resulting in different maximum adsorption capacities.

[0086] Example 2

[0087] Preparation of COF-300@paper (flowchart shown) Figure 8 As shown), including the following:

[0088] 5 mg of COF-300 powder prepared in Example 1 was mixed with 25 mL of ultrapure water and sonicated to obtain a uniformly dispersed suspension. The suspension was then transferred to a Buchner funnel containing filter paper with a diameter of 3.5 cm and filtered under vacuum. Finally, the filter paper matrix loaded with COF-300 was allowed to dry naturally at room temperature to obtain COF-300@paper for later use.

[0089] Characterization of COF-300@paper

[0090] 1. Characterization via SEM

[0091] The morphology of blank filter paper, COF-300@paper, and COF-300@paper after 5 uses was characterized, and the results are as follows: Figure 9 As shown, from SEM Figure 9 As can be seen from (a), its blank filter paper is mainly composed of a fibrous structure with relatively large gaps between the pores. From Figure 9 (b) and (c) show that the COF-300 crystals have a spindle-shaped morphology and are relatively uniformly sized, loaded onto the blank filter paper to form COF-300@paper. Figure 9 (d) As can be seen from the figure, after COF-300@paper was used for 5 spray ionization (PSI) cycles, there were still a lot of COF-300 crystals attached to the filter paper fibers, which to some extent reflects that COF-300@paper has a certain degree of reusability.

[0092] 2. Characterization via XPS

[0093] XPS analysis was performed on COF-300@paper before and after OPPs adsorption, and the results are as follows: Figure 10 As shown, compared with before adsorption, the high-resolution C1s characteristic peak of COF-300 after adsorption of five OPPs shifted by -0.09 to 0.03 eV. Figure 10 (a) The high-resolution P 2p characteristic peak showed a shift of 3.99–14.32 eV. Figure 10 (b) The high-resolution S2p characteristic peak showed a shift of -1.09 to 1.11 eV. Figure 10 (c) This demonstrates that there is an interaction between OPPs and COF-300.

[0094] Example 3

[0095] A method for detecting OPPs based on COF-300@paper (detection process diagram shown) Figure 11 As shown in the figure, the method includes the following steps:

[0096] (1) Sample preparation: Crush the bulk hawthorn dried sample, weigh 1g of sample and disperse it in 20mL of 1% acetic acid aqueous solution, sonicate for 30min, add 10mL of dichloromethane, shake on a shaker for 5min, sonicate for 2min, centrifuge at 8000rpm for 5min, recover the lower organic layer, and obtain the test solution.

[0097] (2) Construction of standard curve

[0098] The COF-300@paper prepared in Example 2 was cut into isosceles triangles with a height of 12 mm, and placed in a series of different concentrations (0.5-200 μg·L⁻¹). -1 OPPs were extracted with a mixed standard sample matrix solution, and after 5 min of natural air drying, they were washed with 1 mL of ultrapure water. After 10 s, they were removed and air-dried. The OPPs were detected using a QTRAP 4500 mass spectrometry system. The distance between the top of the paper and the mass spectrometer inlet was controlled to be 5 mm horizontally and 4 mm vertically. 20 μL of spray solvent ethanol was added to elute the OPPs adsorbed in the COF-300 channels on the surface of the paper matrix.

[0099] During the detection process, the PSI device was installed on a commercial Nanospray Flex source (SCIEX, USA). The mass spectrometry parameters of the QTRAP4500 were optimized as follows: curtain gas: 10 psi; ion source gas 1: 0 Psi; ion source gas 2: 0 Psi; spray voltage 3400 V; IHT (Ion Guide Heater Temperature): 150 °C; collision gas: nitrogen; inlet voltage: 10 V; outlet voltage: 10 V; multiple reaction monitoring (MRM) positive ion mode scanning, scan rate of 10 Da / s; paper angle of 30°.

[0100] Multiple reaction monitoring (MRM) in positive ion mode was used for scanning. The ion pairs, declustering voltage (DP), and collision energy (CE) of the five target OPPs are shown in Table 2. The concentrations (x, μg·L⁻¹) of the five target OPPs were determined. -1 The standard curve results for ) and intensity (y) are as follows Figure 12 And as shown in Table 3: the calibration curves (R) of the five OPPs obtained. 2 ≥0.99) indicates that OPPs have a good linear relationship within the concentration range; the limits of detection (LODs) were calculated using a signal-to-noise ratio (S / N) of 3 and 10 times, respectively, and were in the range of 0.5-1 μg·L⁻¹. -1 Between, and the limits of quantitation (LOQs) are in the range of 1-10 μg·L. -1 The intraday (n=5) relative standard deviation (RSD) of OPPs solutions ranged from 3.1% to 9.4%, and the interday (n=5) RSD ranged from 4.6% to 9.9%.

[0101] Table 2. Ion pairs, declustering voltage (DP), and collision energy (CE) of five target compounds OPPs

[0102]

[0103] Table 3. Linear relationships of OPPs within the concentration range

[0104]

[0105] (3) Determination of OPP content in the sample to be tested

[0106] An isosceles triangle of COF-300@paper with a height of 12 mm was placed in the test solution from step (1) for extraction. After 5 min of natural air drying, it was washed with 1 mL of ultrapure water. After 10 s, it was removed and air-dried. The paper was then detected using a QTRAP 4500 mass spectrometer system. The top of the paper was positioned 5 mm horizontally and 4 mm vertically from the mass spectrometer inlet. 20 μL of spray solvent ethanol was added to elute the OPPs adsorbed in the COF-300 channels on the surface of the paper matrix. The content of OPPs in the test sample was calculated based on the detection results and the standard curve.

[0107] Example 4: Recovery rate, LOD, LOQ, RSD

[0108] 0.2 μg g of each of the six food and medicine homology sample matrices was added. -1 0.5μg g -1 and 1.0μg g -1 The recovery rates of the standard mixed solutions of OPPs were determined, and the results are shown in Table 3:

[0109] Table 4. Content and recovery rate of five OPPs in six actual samples

[0110]

[0111]

[0112] The established COF-300@paper--MS method was used to analyze commercially available food and medicinal samples at concentrations of 0.2, 0.5, and 1.0 μg g. -1 The spiked recovery experiments of five OPPs at three concentrations were conducted. Table 4 shows that the recovery rate of this method ranged from 70.2% to 109.4%, indicating good accuracy. The RSD of the five repeated experiments was less than 11.0%, demonstrating high precision and good repeatability, making this method suitable for OPP residue analysis of food-medicine homologous substances and products. Furthermore, in the red ginseng, rose, and dandelion tea (quality control) sample, three concentrations of dimethoate (0.2, 0.5, and 1.0 μg g) were found.-1 The recoveries were 80.0%, 94.0%, and 104.5%, respectively, with RSDs all less than 8.6%.

[0113] Example 5 Stability and Repeatability

[0114] To further investigate the stability of single-crystal COF-300 particles loaded on paper, the COF-300@paper prepared in Example 2 was stored for 1, 5, 10, 15, and 20 days, and the MRM positive ion mode response values ​​of the OPPs were measured. The results are as follows: Figure 13 As shown;

[0115] from Figure 13 (a) It can be seen that COF-300@paper at 1000 μg·L -1 Paper spray ionization analysis was performed on a mixed solution of five OPPs. The results showed that COF-300@paper had good stability after being stored for different days. The RSD of the five OPPs was around 2.6%.

[0116] The same COF-300@paper in OPPs solution at 1000 μg·L -1 Paper spray ionization analysis was performed at a concentration of [value] for six adsorption-desorption cycles, and the results are as follows: Figure 13 As shown in (b), after repeated use (≥5 cycles), the RSD was 8.1%, and the performance of COF-300@paper material decreased, indicating that the synthesized COF-300@paper has good stability and reusability, and can be stored for a long time.

[0117] Example 6 Parameter Optimization

[0118] At 1 mg·L -1 The OPPs standard mixed solution was used as the test object, and the test was performed according to the method in Example 3; the details are as follows:

[0119] 1. The impact of COF-300 load on OPP signal strength

[0120] Different masses of COF-300 material (0, 2.5, 5, 7.5, 10, 12.5 mg) were added to beakers and dissolved in 25 mL of ultrapure water. The solutions were sonicated for 30 min to ensure uniform dispersion in the aqueous solution. The solutions were then poured into a funnel containing 3.5 cm diameter filter paper for filtration to obtain the paper matrix COF-300@paper. The prepared paper matrix (COF-300@paper) was air-dried and used for online detection by paper spray mass spectrometry. The optimal amount of COF-300 was determined based on the signal intensity of COF-300@paper in the multiple reaction monitoring (MRM) mode of OPPs.

[0121] The results are as follows Figure 14 (a) It was observed that the PSI (paper spray ionization) signal first increased and then decreased with increasing COF-300 loading. The recovery rate of the five OPPs was highest when the COF-300 loading was 5 mg. This is because the crystalline COF-300 particles can adhere to the porous fiber paper matrix, and the 3D through-pores significantly improve the mass transfer efficiency with increasing COF-300 particle size; and the active sites (C=N) on the surface of COF-300 enhance the interaction force with the target OPPs, thus improving the recovery rate of OPPs. However, with further increases in COF-300 loading, the excess COF-300 crystalline particles cannot adhere firmly to the filter paper, and some crystalline particles detach, resulting in a decrease in elution efficiency and spray efficiency, a decrease in the MRM response value of PSI, and a decrease in the recovery rate of OPPs.

[0122] 2. The effect of spray voltage on OPP signal strength

[0123] Six voltages (2500, 2800, 3100, 3400, 3700, and 4000V) in the range of 2500V to 4000V were tested on the COF-300@paper substrate prepared in Example 2. The optimal spraying voltage conditions were finally determined by analyzing the signal response intensity of the COF-300@paper modified material to the multiple reaction monitoring (MRM) mode of organophosphorus pesticides (OPPs).

[0124] The results are as follows Figure 14 (b) It was observed that the PS signal first increased and then decreased with increasing spray voltage. The signal strength was strongest when the spray voltage was set to 3400V, indicating that the atomization efficiency of the target analyte OPPs ions was best at 3400V. If the applied voltage is too low, the surface tension of the liquid cannot be overcome, thus failing to form atomization effectively and resulting in reduced ionization efficiency. If the applied voltage is too high, it may lead to discharge phenomena, which in turn cause local high temperatures. This high-temperature environment can damage the molecular structure of the target analyte, causing it to fragment excessively and ultimately producing unintended pyrolysis products within the ion source.

[0125] 3. The effect of spray solvent on OPPs recovery rate

[0126] Five solvents—methanol, ethanol, isopropanol, n-hexane, and acetonitrile—were selected and added dropwise to the COF-300@paper matrix prepared in Example 2 for testing. By comparing the signal response intensity of the COF-300@paper modified material to the multiple reaction monitoring (MRM) mode of organophosphorus pesticides (OPPs), the optimal solvent selection was finally determined.

[0127] The results show that Figure 14As shown in (c), in the comparative tests of five spray solvents—methanol, ethanol, isopropanol, n-hexane, and acetonitrile—the paper spray ionization (PS) signal intensity of the nonpolar solvent n-hexane was significantly lower than that of the other solvents, indicating that nonpolar solvents are not suitable for paper spray mass spectrometry analysis. Among the polar solvents (methanol, acetonitrile, isopropanol, and ethanol), ethanol exhibited the highest signal intensity and OPPs recovery rate when used as the spray solvent.

[0128] 4. The effect of the tip angle of the COF-300@paper matrix on the signal intensity of OPPs

[0129] The effect of the apex angle (10°, 20°, 30°, 40°, 50°, 60°) of the COF-300@paper triangular paper matrix on detection sensitivity was investigated. By analyzing the signal response intensity of the COF-300@paper modified material to the multiple reaction monitoring (MRM) mode of organophosphorus pesticides (OPPs), the optimal paper matrix geometry parameters were finally determined.

[0130] The results are as follows Figure 14 (d) It was observed that the PSI signal exhibited a "quasi-triangular asymmetric distribution" trend with increasing tip angle. When the tip angle was set to 30°, the MRM signal of OPPs was the strongest, and the recovery rate of OPPs was the highest. This is because the signal intensity, jet current, and electric field at the nozzle all depend on the angle of the paper tip. The electric field density of the paper tip cut into a small angle is higher, which is conducive to generating spray. However, the corresponding paper area is also relatively smaller, resulting in fewer extracted OPPs and a smaller PSI signal. As the angle increases to 30°, the extracted OPPs increase, and the PSI signal intensity is the highest. The larger the angle, the more difficult it is to excite ionization, and the lower the PSI signal. When the angle increases to a certain extent, although ionization is difficult, the amount of extracted OPPs is greater, leading to an increase in the PSI signal again.

[0131] Comparative Example 1

[0132] A comparison with existing OPPs analysis methods is shown in Table 5:

[0133] Table 5 Comparison of this method with other OPPs residue determination methods.

[0134]

[0135] The results in the table show that this method has low limits of detection and quantitation, and has the advantages of high efficiency, speed, and low solvent consumption. The extraction time for the five OPPs is short (COF-300 can achieve approximately 90% equilibrium adsorption of the five OPPs in about 5 minutes). Furthermore, this method is simple to operate and has a low matrix effect, making it suitable for the analysis of OPP residues in complex food matrix samples.

[0136] [1]Farajzadeh M A,Mogaddam M R A,Aghdam S R,et al.Application ofelevated temperature-dispersive liquid-liquid microextraction fordetermination of organophosphorus pesticides residues in aqueous samplesfollowed by gas chromatography-flame ionization detection[J].Food Chemistry,2016,212:198-204.

[0137] [2]Shakourian M,Yamini Y,Safari M.Facile magnetization of metal-organic framework TMU-6 for magnetic solid-phase extraction oforganophosphorus pesticides in water and rice samples[J].Talanta,2020,218:121139.

[0138] [3]Tan L,Li W,Li H,et al.Development of surface imprinted core-shellnanoparticles and their application in a solid-phase dispersion extractionmatrix for methyl parathion[J].Journal of Chromatography A,2014,1336:59-66.

[0139] [4]Chang H W,Chen C L,Chen Y H,et al.Electrochemical organophosphoruspesticide detection using nanostructured gold-modified electrodes[J].Sensors,2022,22(24):9938.

[0140] [5]Zhou Q, Wang L, Pan C, et al. Multi-pesticides analysis in honeysuckleand chrysanthemums based on nano-material modified QuEChERs coupled with HPLC-MS / MS[J]. Microchemical Journal, 2025:112999.

[0141] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for detecting organophosphorus residues in food and medicine homologous products based on paper spray mass spectrometry, characterized in that, The method includes the following steps: (1) Sample pretreatment Weigh the sample to be tested and disperse it in an aqueous acetic acid solution. After sonication, add dichloromethane, shake, centrifuge, and recover the organic layer to obtain the test solution. (2) Determination of organic phosphorus content in the sample to be tested The COF-300@paper paper base was placed into the test solution in step (1) for extraction. After extraction, it was dried and sprayed with ethanol. The COF-300@paper paper base was then added dropwise and detected by mass spectrometry. The content of OPPs in the test sample was calculated based on the detection results and the standard curve. The preparation of the COF-300@paper base involves mixing COF-300 powder with ultrapure water to obtain a uniformly dispersed suspension, then transferring it to a Buchner funnel containing filter paper, and filtering it under vacuum to obtain a filter paper matrix loaded with COF-300. After drying, the COF-300@paper base is obtained.

2. The method according to claim 1, characterized in that, The organophosphates include one or more of the following: phosmet, phosmet, dimethoate, phosmet, and acephate.

3. The method according to claim 1, characterized in that, The medicinal and edible products include one or more of the following: hawthorn, ginseng and barley tea, red ginseng and rose vitality tea, red ginseng, rose and dandelion tea, goji berries, and ginseng.

4. The method according to claim 1, characterized in that, The amount of COF-300 loaded on each 3.5cm diameter filter paper on the COF-300@paper base is 2.5 to 12.5 mg.

5. The method according to claim 1, characterized in that, The COF-300@paper base in step (2) is an isosceles triangle with a vertex angle of 10 to 60°.

6. The method according to claim 1, characterized in that, The COF-300 powder is obtained by reacting terephthalaldehyde (BDA) and tetrakis(4-aminophenyl)methane (TAM) at a temperature of 40–45°C for 36–48 hours.

7. The method according to claim 1, characterized in that, The specific preparation method of the COF-300 powder is as follows: (1) Mix BDA, 1,4-dioxane and CF3CH2NH2, vortex, and add CF3COOH to obtain reaction solution A; (2) Dissolve TAM in 1,4-dioxane to obtain reaction solution B; (3) Add reaction solution B to reaction solution A, filter, and let stand at 40-45℃ for 36-48h. After the reaction is completed, extract the synthesized crystals in 1,4-dioxane and tetrahydrofuran by Soxhlet extraction, dry, and obtain yellow crystals, i.e. COF-300 powder.

8. The method according to any one of claims 6 or 7, characterized in that, The mass ratio of BDA to TAM is 10-15:

20.

9. The method according to claim 1, characterized in that, The mass spectrometry parameters of the mass spectrometry system described in step (2) are as follows: curtain gas: 10 psi; ion source gas 1: 0 Psi; ion source gas 2: 0 Psi; spray voltage 3400 V; IHT: 150 °C; collision gas: nitrogen; inlet voltage: 10 V; outlet voltage: 10 V; multiple reaction monitoring (MRM) positive ion mode scanning, scan rate 10 Da / s; paper angle 30°.

10. The application of the method according to any one of claims 1 to 9 in food safety monitoring.

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